Chronic pain and clicking about the distal radial ulnar and ulnocarpal joint associated with weakness of grip and a subjective sensation of wrist instability are frequently results of a healed Colles fracture, a dislocated or subluxed distal radial ulnar joint, arthritic involvement of the wrist, or more frequently, a seemingly rather insignificant wrist injury. Many surgical and nonsurgical treatments have been suggested to deal with these symptoms without full knowledge of the cause of the symptoms. This inadequacy of knowledge is a direct result of the lack of understanding of anatomic and biomechanical interrelationships of the wrist components in normal and pathological situations. This research program proposes to further pursue our investigation into the anatomy and function of the ulnar aspect of the wrist. Using the techniques developed in the ongoing Biomechanical Study of the Radial Ulnar Carpal Joint, radioulnar carpal, and intercarpal forces and pressures will be studied in the intact wrist as well as surgically altered wrists (e.g. ulnar shortening, distal ulnar resection, distal ulnar Silastic replacement, carpal resections,....). The analysis of the effect of these operative procedures on the normal wrist biomechanics would lead to recommendations regarding the efficacy of previously recommended treatment modalities for different wrist problems. Improved treatment protocols for specific pathological conditions of the wrist would hopefully be forthcoming based on sound biomechanical principles with predictable long-term results.